feat: authoritative extraction from ResourceNode on task completion

Phase 3 of ResourceNode migration:
- Add apply_resource_delta to SimVillage for clean resource changes
- Extract from reserved ResourceNode on task completion instead of
  hard-coded apply_npc_task for gather_food/gather_wood
- Detect depleted/unavailable targets on arrival and replan

simulation/SimulationManager.gd

@@ -86,9 +86,17 @@ func simulate_tick() -> void:
 			var needs_immediate_food_after_gather := npc.should_eat_immediately_after_task()
 
 			if npc.target_id != &"":
+				var node := ResourceNode.get_by_id(npc.target_id)
+				if node != null:
+					var extracted := node.extract()
+					if extracted > 0:
+						village.apply_resource_delta(node.resource_id, extracted)
+						if DEBUG_LOGS:
+							print("[SimulationManager] ", npc.npc_name, " extracted ", extracted, " ", node.resource_id, " from ", node.node_id)
 				release_npc_reservation(npc.id)
+			else:
+				village.apply_npc_task(npc)
 
-			village.apply_npc_task(npc)
 			village_was_changed = true
 
 			npc.task_complete = true
@@ -161,6 +169,15 @@ func notify_npc_arrived(npc_id: int) -> void:
 				return
 
 			if npc.task_state == SimNPC.TASK_STATE_TRAVELING:
+				if npc.target_id != &"":
+					var node := ResourceNode.get_by_id(npc.target_id)
+					if node == null or not node.can_extract():
+						if DEBUG_LOGS:
+							print("[SimulationManager] ", npc.npc_name, " arrived but target ", npc.target_id, " is unavailable, replanning")
+						release_npc_reservation(npc.id)
+						npc.task_state = SimNPC.TASK_STATE_IDLE
+						return
+
 				npc.start_working()
 
 				if DEBUG_LOGS: